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e6459606 PA |
1 | /* ----------------------------------------------------------------------- * |
2 | * | |
3 | * Copyright 2012 Intel Corporation; author H. Peter Anvin | |
4 | * | |
5 | * This file is part of the Linux kernel, and is made available | |
6 | * under the terms of the GNU General Public License version 2, as | |
7 | * published by the Free Software Foundation. | |
8 | * | |
9 | * This program is distributed in the hope it will be useful, but | |
10 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | * General Public License for more details. | |
13 | * | |
14 | * ----------------------------------------------------------------------- */ | |
15 | ||
16 | /* | |
17 | * earlycpio.c | |
18 | * | |
19 | * Find a specific cpio member; must precede any compressed content. | |
20 | * This is used to locate data items in the initramfs used by the | |
21 | * kernel itself during early boot (before the main initramfs is | |
22 | * decompressed.) It is the responsibility of the initramfs creator | |
23 | * to ensure that these items are uncompressed at the head of the | |
24 | * blob. Depending on the boot loader or package tool that may be a | |
25 | * separate file or part of the same file. | |
26 | */ | |
27 | ||
28 | #include <linux/earlycpio.h> | |
29 | #include <linux/kernel.h> | |
30 | #include <linux/string.h> | |
31 | ||
32 | enum cpio_fields { | |
33 | C_MAGIC, | |
34 | C_INO, | |
35 | C_MODE, | |
36 | C_UID, | |
37 | C_GID, | |
38 | C_NLINK, | |
39 | C_MTIME, | |
40 | C_FILESIZE, | |
41 | C_MAJ, | |
42 | C_MIN, | |
43 | C_RMAJ, | |
44 | C_RMIN, | |
45 | C_NAMESIZE, | |
46 | C_CHKSUM, | |
47 | C_NFIELDS | |
48 | }; | |
49 | ||
50 | /** | |
51 | * cpio_data find_cpio_data - Search for files in an uncompressed cpio | |
52 | * @path: The directory to search for, including a slash at the end | |
53 | * @data: Pointer to the the cpio archive or a header inside | |
54 | * @len: Remaining length of the cpio based on data pointer | |
55 | * @offset: When a matching file is found, this is the offset to the | |
56 | * beginning of the cpio. It can be used to iterate through | |
57 | * the cpio to find all files inside of a directory path | |
58 | * | |
59 | * @return: struct cpio_data containing the address, length and | |
60 | * filename (with the directory path cut off) of the found file. | |
61 | * If you search for a filename and not for files in a directory, | |
62 | * pass the absolute path of the filename in the cpio and make sure | |
63 | * the match returned an empty filename string. | |
64 | */ | |
65 | ||
0db0628d | 66 | struct cpio_data find_cpio_data(const char *path, void *data, |
e6459606 PA |
67 | size_t len, long *offset) |
68 | { | |
69 | const size_t cpio_header_len = 8*C_NFIELDS - 2; | |
70 | struct cpio_data cd = { NULL, 0, "" }; | |
71 | const char *p, *dptr, *nptr; | |
72 | unsigned int ch[C_NFIELDS], *chp, v; | |
73 | unsigned char c, x; | |
74 | size_t mypathsize = strlen(path); | |
75 | int i, j; | |
76 | ||
77 | p = data; | |
78 | ||
79 | while (len > cpio_header_len) { | |
80 | if (!*p) { | |
81 | /* All cpio headers need to be 4-byte aligned */ | |
82 | p += 4; | |
83 | len -= 4; | |
84 | continue; | |
85 | } | |
86 | ||
87 | j = 6; /* The magic field is only 6 characters */ | |
88 | chp = ch; | |
89 | for (i = C_NFIELDS; i; i--) { | |
90 | v = 0; | |
91 | while (j--) { | |
92 | v <<= 4; | |
93 | c = *p++; | |
94 | ||
95 | x = c - '0'; | |
96 | if (x < 10) { | |
97 | v += x; | |
98 | continue; | |
99 | } | |
100 | ||
101 | x = (c | 0x20) - 'a'; | |
102 | if (x < 6) { | |
103 | v += x + 10; | |
104 | continue; | |
105 | } | |
106 | ||
107 | goto quit; /* Invalid hexadecimal */ | |
108 | } | |
109 | *chp++ = v; | |
110 | j = 8; /* All other fields are 8 characters */ | |
111 | } | |
112 | ||
113 | if ((ch[C_MAGIC] - 0x070701) > 1) | |
114 | goto quit; /* Invalid magic */ | |
115 | ||
116 | len -= cpio_header_len; | |
117 | ||
118 | dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4); | |
119 | nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4); | |
120 | ||
121 | if (nptr > p + len || dptr < p || nptr < dptr) | |
122 | goto quit; /* Buffer overrun */ | |
123 | ||
124 | if ((ch[C_MODE] & 0170000) == 0100000 && | |
125 | ch[C_NAMESIZE] >= mypathsize && | |
126 | !memcmp(p, path, mypathsize)) { | |
127 | *offset = (long)nptr - (long)data; | |
128 | if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) { | |
129 | pr_warn( | |
130 | "File %s exceeding MAX_CPIO_FILE_NAME [%d]\n", | |
131 | p, MAX_CPIO_FILE_NAME); | |
132 | } | |
133 | strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME); | |
134 | ||
135 | cd.data = (void *)dptr; | |
136 | cd.size = ch[C_FILESIZE]; | |
137 | return cd; /* Found it! */ | |
138 | } | |
139 | len -= (nptr - p); | |
140 | p = nptr; | |
141 | } | |
142 | ||
143 | quit: | |
144 | return cd; | |
145 | } |